Clamping device



5, 1933; P. J. MQCULLOUGH 1,922,446

CLAMPING DEVICE 2 Sheets-Sheet 1 Filed March 7, 1950 Aug. 15, 1933. P. J. MOCULLOUGH CLAMPING DEVICE Filed March 7, 1950 2 Sheets-Sheet 2 av p .k

Patented Aug. 15, 1933 PATENT OFFICE CLAMPING DEVICE 7 Paul J. McCullough, St. Lcuis,-Mo., assignor to Scullin Steel 60., St. Louis, M0,, a Corporation of Delaware Application March '7, 1930. Serial No. 433,915

3 Claims.

This invention relates to clamping devices, and is illustrated as embodied in a clamping device for holding flasks in positionon stripping plates of molding machines.

The 'lustrated embodiment of the invention includes a movable jaw arranged to press the parts to be held against a fixed jaw, the movable jaw being turned by means of a square piston on a helical square sectioned piston rod in a square sectioned fluid-pressure chamber.

One object of this invention-is to provide a device capable of dependably holding a flask weighing 41,000 pounds when loaded with sand to a stripping plate of a molding machine. In 'the course of operating the molding machine, the flask is raised and dropped three inches one hundred times a minute. In another step of the operation, the stripper plate and the flask supported are rolled over. Under such condi-. tion, the clamps must be able to support the entire length of the flask.

Another object of the invention is to provide a compact device which will operate automatically to clamp into position whatever flask may be placed on the stripper plate.

A further object of the invention is to provide an automatic clamping device which will perform its function independently of the means used for attaching the clamp to the stripper plate and will therefore avoid putting strain on the attaching means during its operation and will obviate the danger of its working loose.

. A further object or the invention is to provide a compact and efficient clamp which will press solidly together the objects to be clamped but will be substantially self-locking and hence once in position will resist almost unlimited opening force.

Other objects of the invention will appear from the following description, drawings and claims.

In the drawings, in which like numerals are used for similar parts throughout- Figure 1 is an end View of the clamping device, illustrating more or less diagrammatically its relation to a stripper plate and flask;

Figure 2 is a side elevation of the clamping device, and further showing its relation to the apparatus on which it is to be used;

l Figure 3 is a perspective View of the clamping device with some parts separated or broken away; and

Figure 4 is a longitudinal section through the clamping device.

In Figure 1, the clamping device 10 is illustrated as attached to a stripping plate 12, which according to the common practice is bolted to the molding table therebelow but not shown. A flask 14 is shown in position upon the stripping plate. These flasks are commonly loaded with sand, reciprocated one hundred times a minute, and rolled over together with the stripping plate and molding table. They are held against lateral movement by dowel pins (not shown) and are held in place on the dowel pins and on the stripping plate by jaws 16 and 18 of the clamps 10. Preferably two clamps are provided at diagonally opposite corners of the stripping plate. Only one. however has been shown and of course, if desired, some other retaining means could be used in place of the other. 7 V

I'he jaws l8 fit underneath the flange 20 of the stripping plate 12, and the jaw 16 swings down on top of the flange 22 of the flask, which is immediately above the flange 20. Thusit is seen that this invention makes use of the fact that the bottom flanges 22 of all the flasks are of the same size, with the result that'when the jaw 16 is swung away, the flask 14 may be removed and another flask of a different size may be put in its place'and held equally well.

The clamp is held in place by the front plate 24 and back plate 26,.which may be forced against the stripper plate by a single nut and bolt, as shown best in Figure 1. The clamping device proper is best disclosed in Figures 3 and 4, in which it is seen that the jaw 16 .is rigidly attached to a piston rod 30 which rotates in bearings 32, preferably of a frictionless type. One bearing may of course be located in the back plate 26. The jaws 18 really constitute one jaw in two parts, one on the back plate 26 and one on the front plate 24 on either side of the jaw 16. The two jaws 18 are rigidly secured in spaced positions as by means of bolts or cap screws 34 (in Figure 2) extending through hollow spacing legs 36. The jaw 16 revolves about a hub 38 which may be integral therewith and which rotates within a socket in plates 24: and 26. Thus in the event of a weakening or breaking of one of the bearings, the jaw 16 would still be held in proper relation with jaws 18. It should be noted that the jaws 16 and 18 together form a clamp of pincher-like action.

The piston rod 30 extends through the back plate 26, as indicated best in Figure 4, and through the square pressure chamber 40 to its rear bearing in the end plate 42. This plate 42 also forms a back end of the pressure chamber 40. Bolts 44 may be provided to hold the pressure chamber back plate and end plate in proper relation, though of course the chamber may be constructed as a unit.

That portion of the piston rod 30 which lies within the pressure chamber is square in cross section and is given a twisted shape, as shown. The pitch of twist is preferably about one.- quarter turn in six inches. may be varied to change the ratio of forces or the degree of self-locking. Mounted on said piston rod is a piston 46 which is of a shape to flt fairly closely about the piston rod andalso closely into the pressure chamber 40. In other words, the piston has a helical square crosssectioned hole therethrough and is square in outer cross-section.

It is thus clear that as the piston is moved longitudinally in the pressure chamber, the piston rod is rotated thereby. The piston is preferably provided with packing 48 on both faces, the packing being cut both at the outside to contact with the pressure chamber and at the inside to contact with the piston rod. The packing is held in place by members 50 which are held to the piston as by means of bolts 52 extending through the same. The piston is caused to move backward by pressure which may be introduced through the, connections 54.

Between the members 52 and the packing 48 may be inserted squares from a copper sheet of .0120 inch thickness, out to acquire spring as with the grain on a bias of 30 to 45 with respect to the outer edges, and thus also biased with respect to the edges along the piston rod. Of course any known packing may be used, or the clamp will work satisfactorily without any packing, though with a leak of air.

The operation of the apparatus may be summarized as follows:

The flask is placed upon the stripping plate, and fluid such as air or water is forced in through one of the connections 54, at the right in Figure 4, to shove the piston 46 toward the front end of the fluid pressure chamber (left in Figure 4). The piston is restrained from rotation by its outer shape and the shape of the pressure chamber. Likewise, due to the pistons inner square-helical shape and the corresponding outer shape of the piston rod 30, the piston rod is rotated by the longitudinal movement of the piston. This rotation of the piston rod rotates the'jaw 16 which presses the flange 22 of the flask 14 against the flange 20 of the stripper plate 12, thus holding the flasks rigidly in position.

This clamping device has numerous advantages over other types of clamps. Chief among them is the fact that due to the screw action on the piston rod, the clamp is at least partially self-locking so that once in holding position it will not be forced out. As there is prac- Though this pitch tically no resistance to the closing of the jaws until they substantially reach their limit, there will be very little wear on the moving parts, and hence the device would be of extremely long life. Lubricating means of course can be provided to increase its life. The pincher-like action of the jaws saves the attachment bolt from additional strain, and hence prevents the clamping device working loose from the stripper plate. This quality may be explained by stating that the actuating force and its reaction are transmitted solely to the jaws.

Obviously the actuating device could be used with other types of jaws and for many other uses in which rotation or self-locking is desired.

It is to be understood that many other embodiments of the invention, including some in improved form, will be apparent and in the course of time will be devised by those skilled in the art. My invention includes all of these which come within the spirit of the following claims, construed as broadly as the prior art will permit. v

I claim:

1. A flask clamping device for molding machines comprising a pair of jaws, one of which is rigidly connected to a fluid pressure casing which is square in cross-section, a piston which is square in cross-section slidably mounted in said casing, said piston having a hole therethrough which square in cross-section, the piston being slidably mounted on a piston rod which is helically shaped and square in cross section and which is rotated by longitudinal movement of the piston and which rotates the other jaw which is rigidly attached thereto.

' 2. A flask clamping device for molding machines including a pair of rotatable jaws, means for rotating one of said jaws including a fluid pressure chamber having non-circular crosssections, a piston of corresponding cross-section, a piston'rod of non-circular cross-section extending through a correspondingly shaped hole in the piston, said chamber and piston rod having a relative twist, and each being connected to one of the jaws.

3. A flask clamping device for molding machines comprising a pair of jaws, one of which is rigidly connected to a fluid'pressure casing which is square in cross-section, a piston which is square in cross-section slidably mounted in said casing, said piston having a hole therethrough which is square in cross-section, the piston being slidably mounted on a piston rod which is helically shaped and square in crosssection and which is rotated by longitudinal movement of the piston and which rotates the other jaw which is rigidly attached thereto, the pitch of. the helix being such as to prevent movement of the piston by rotation of the piston rod.

PAUL J. McCULLOUGH. 

